Inexpensive “dipstick” tests for diseases

MENLO PARK, Calif. – Scientists from the Center for Infectious Diseases at the Silicon Valley-based research institute
SRI International are developing a simple test for some parasitic diseases that
could help poorer parts of the world combat the infections and poverty they engender.
The new straightforward test uses UV light to highlight a particular dye that has
been found to act as a biomarker for all these parasitic diseases.

“This tool could have an important positive impact on people’s
lives,” said Ellen Beaulieu, a medicinal chemist at the center’s Biosciences
Div. “As we advance our development, we will seek collaborations to move the
tool into clinical use – for example, with foundations focused on global health
initiatives.”

Sleeping sickness, Chagas disease and leishmaniasis cause tens
of thousands of deaths each year and are particularly prevalent in developing countries
where access to health care is limited. Figures from the Seattle Biomedical Research
Institute indicate that more than 60 million people in 36 countries of sub-Saharan
Africa are threatened by sleeping sickness.

Chagas disease has been cited as the leading cause of heart disease
in Central and South America, affecting about 25 percent of the Latin American population,
and leishmaniasis endangers 350 million people in 88 countries in the tropics, subtropics
and Middle East.

These diseases are closely related members of what scientists
know as the Trypanosomatidae family. One existing test for diagnosing these diseases
involves taking a blood sample from a patient and examining it under a microscope
for the parasites at the root of the diseases. But the process is time-consuming
and labor-intensive, making rapid screening in rural locations troublesome.

Another method relies on the detection of a biomarker from the
patient’s own immune response, which, although a very sensitive method of
detection, can require expensive medical equipment and highly trained technical
personnel.

A specially formulated dye glows after exposure to ultraviolet light
to reveal the presence of a parasite metabolite. Courtesy of SRI International.
The new test involves using UV light to reveal the presence of
a parasitic marker, which has been tagged with a specially developed dye. Initial
laboratory tests can produce results in as little as one hour, but the goal is to
develop a “dipstick” version that will enable detection using a simple
paper strip, such as those used in urine tests for diabetes.

A simple dipstick test could allow health care workers in remote
areas to diagnose the diseases by dipping the strip in a drop of the patient’s
blood and exposing it to UV light from a simple, handheld lamp.

“This method has the advantage of using an inexpensive dye,
which is detected using an inexpensive instrument, and would eliminate the need
for technical training for accurate screening diagnosis,” Beaulieu said.

SRI researchers are in the development stage for determining the
optimal dye for the clinical application.

“Our current diagnostic protocol is a solution-based approach,
and we are still at the stage of optimizing the dyes for this purpose,” Beaulieu
said. “Once a dye has been identified that meets our optimal criteria, we
will begin the development of a dipstick version.”